Solenoid



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INVENTOR. M7/7m 4. fag SYM/sl ATTORNEY w. A. RAY

SOLENOID Filed OCZ. l5, 1956 Nov. 2, 1937.

I Patented Nov. 2, 1937 UNITED STATES PATENT FFlcE SOLENOID California REISSUD APR 8 1941 applicati@ october-1s, 193s, serial No. 195,100

1Claim.

This invention relates to an improved construction for an electro-magnetic operator, commonly termed a solenoid. The present invention relates to improvements in the construction of those devices generally disclosed by me in my copending applications Serial No. 635,886, illed October 3, 1932, and Serial No. 92,748, tiled July 27, 1936.

In the construction and manufacture of a suitable electro-magnetic operator for use upon alternating current, I have experienced considerable dilculty in ridding the device of humming. For example, in assembling the control device/disclosed in my Patent No. 2,046,882, of July '7, 1936,

.it was found that some two to four hours time was necessary to assemble the solenoid valve 23 in the structure shown in said patent to ensure that the solenoid 'would'be' free from hum. This assembly time for this single unit raised the assembly cost for the valve structure of said patent beyond all practical reason.

After considerable investigation into the cause of L,the humming and after many trials in an attempt to overcome this undesirable characteristic, I have at last found a construction which obviates the humming, enabling the electro-magnetic operator to be assembled as rapidly as an assembly mechanic can put the proper parts' together. 'I'his has enabled the assembly of the g aforementioned valve of my patent to be made with much greater ease, since the time required in connection with the magnetic operator 23 is a.

matter of minutes, as compared to hours.

Briefly summarizing the results of my investigation into the causes of humming, it was my nding that humming was due to transverse displacement of one end of the solenoid plunger.

This occurred even though the other end of the plunger was xed against such transverse movement and even though all parts of the electromagnetic operator, including the washers, plunger and associated metal parts were carefully machined to tolerances so restricted as to be impractical in-commercial production.

I found that it was necessary to keep the f plunger axially aligned in the magnetic centerof the axial passage through" the coil of the electro-magnetic operator. This centering I accomplished in a very simple manner, as will presently appear hereinafter, wherein I have disclosed the i preferred construction embodying the discovery of this invention. Itis in general the broad object of the present invention to improve upon the construction of an electro-magnetic operator to the end that humming of said operator, when utilized in con- (Ql. F15-338)- junction with alternating current, is eliminated.

A further object of the present invention is to provide .an improved solenoid construction enabiing an effective electro-magnetic operator to be constructed by commercial manufacture to 5 provide a cheap, readily assembled and yet satisfactory operator.

The invention includes other objects and features of advantage, some of which, together with the foregoing, will appear hereinafter, wherein l0 vthe present preferred construction of this inven* tion is set forth.

In the drawing accompanying and forming a part hereof:

Figure l is a section taken through a solenoid l5 structure including the present preferred construction.

Figure 2 is a cross section through the structure of Figure 1. 1

Figure 3 is a cross section through a solenoid in 20 which the solenoid plunger floats.

The actuator of the present invention is provided with a base 6 having a. threaded extension 1 so that the actuator can be suitably attached to a housing, such as that including a valve or other 25 device to be operated. A non-magnetic tube 8 of brass, monel or the like is secured to the base 6. An insert I2 is secured as at I3 to the tube, the insert including an extension I4 threaded to receive a nut I6. A suitable housing, generally in- 30 dicated at I'l, is mounted upon and is secured in place upon the threaded extension I4 by means of the nut, this housing including an inlet I8 for attachment of a,` conduit including lead-in Wires.

The insert I2 is. made of non-magnetic ma- 35 terial, but carries a. ring I9 of magnetic material. This ring is grooved as at 20 and the tube 8 is rolled in to nt this groove and to retain the magnetic ring in place. An insert 2I of magnetic material is carried on the insert I2, the

insert 2I-projecting beyond the insert I2 and being formed at 22 to center the solenoid plunger generally indicated by numeral 24. The solenoid plunger is a composite structure, including an outer magnetic shell 23 or primary core ap- 45 proximating in size the ring I9. Mounted within and adjacent the upper end is a non-magnetic plug 30 providing a shading ring. Inserted within this plug is a magnetic plug 26 providing a secondary core. 'Ihe magnetic plug 50 23 and non-magnetic plug 30 are concentrically apertured longitudinally to release any fluid that might be trapped between the plunger and the stop. In addition, the shell 23 is apertured as at 25. l

Slidably mounted in the bottom portion of the solenoid is a stud 2l. This stud is retained ,in place by a sleeve 28 of magnetic material screwed into the bottom of the sleeve 23. Stud 2l has a head 29 thereon against which rests a light spring tl. rIhis spring urges stud 2l upwardly to permit the plunger to rise before it begins to lift stud 2l and the structure attached thereto, for example, a valve.

The electromotive force is supplied by a coil 33 formed upon a spool ttl. The spool 3ft is positioned between magnetic washers 35 and 2lb, these washers being mounted upon and including angular portions 3l extending along the tube t.

ln operation, the current now through the coil reaches a maximum flow at the peak of the sine Wave, and a minimum or Zero flow at the end of each half cycle. Actually, there is a large ow of current provided in one direction for a fraction of a second, followed by cessation of current iiow when the half cycle changes or the current reverses. The present invention enables an effective force to be maintained upon the solenoid plunger at all times and even though the current for. an instant is Zero and subsequently reverses. This substantially constant flux flow to the plunger enables the humming noise to be overcome.

lt is the discovery of the present invention that the humming 4noise is due to vibration of the solenoid plunger, particularly in that region adjacent the stud 2l. Since the plunger is positioned at the other end by engagement of parts 22 and 2t, I have found that by placing a ring lll of non-magnetic material, such as copper, brass, or dural, around the base of the solenoid plunger, the humming can be obviated. This l .attribute to the shielding eect, on the base of the plunger, from the adjacent lines of flux from the washer 35 and its portion 3l.

ft is very difficult to manufacture an electromagnetic operator of the type herein dealt with which is symmetrical about the solenoid plunger axis. For example, any slight excess thickness in one side of angular portion 3l will result in a greater ow of magnetic lines of force from that side than from the opposite side. As a consequence, the solenoid plunger attempts to position itself in the magnetic center. However, since the device is being operated upon alternating current, the ilux lines are constantly changing, with the result that the plunger is always attempting to follow this change and take up a new position. By providing the ring di about the base of the plunger, the inequalities are more or less equalized, so that such careful attention aooaioo to super-accurate machining is not necessary. As a matter of fact, have found that superaccurate machining without the present invention and the structure evolved thereby -was not sufcient, for solenoid operators manufactured under the most careful machining and supertolerances were extremely disappointing in that they hummed just as loudly as those taken from the commercial assembly line.

The present invention therefore enables a relatively cheap and inexpensive electro-magnetic operator to be provided. For example, it enables me to successfully utilize a square type of solenoid plunger inside of the round guide tube t, to avoid a dash pot effect and to enable the plunger to rise quickly. The ring ll is merely slipped over the plunger and secured thereto as by spreading the end of the plunger slightly, or by otherwise securing the ring securely on the plunger.

The invention is also applicable to solenoids as in Figure 3 wherein the plunger 5l oats freely. The insert l2 is cut off so the plunger is limited in its rise by the spring 3l and stud 2l. The

' portion 3l on the upper washer' extends down slightly more than in Figure l to ensure fiux now to lift the plunger 5l which. is made as light in weight as is possible. The ring di is positioned about the plunger base. I

It is of course readily apparent to those skilled in the art that various modifications can be made without departing from the scope of the appended claim.

l claim:

lin a device of the character described, a coil having a passage therethrough, magnetic washers at either end of said coil, a solenoid plunger movable through said passage axially upon energization of said coil into engagement with stop means positioned at one end of said passage to align that end of the plunger in a definite single position axially of said passage, said plunger including an inner magnetic member encased at least partially by a non-magnetic member and an outer magnetic member extending substantially between said washers when said plunger engages said stop, said members being xedly joined together into a single unit movable as such, said inner magnetic member engaging said stop means, and a non-magnetic sleeve carried by the plunger and positioned thereon to distribute more evenly flux from one of said washers adjacent the other endof the plunger and maintain said other plunger end in a single position in said passage whereby humming is absent. 

